Roller press apparatuses are used for grinding different kinds of particulate materials such as e.g. limestone, cement clinker, slag sand, old concrete and additionally materials of the mineral/mining industry.
Traditional roller press apparatuses often have an unfavorable throughput-to-speed behavior in the sense that an increase of the peripheral velocity of the rollers is only possible up to a certain point. Thereafter, a further increase of the velocity does not result in a corresponding increase of the throughput. One explanation could be the difficulty in obtaining an acceleration of the material which is to be ground to achieve a speed essentially corresponding to the peripheral velocity. Further, vibration problems frequently arise due to uneven supply of material with different sizes of the particles of the material supplied to the gap of the roller press and/or air being entrained in the particulate material delivered to the gap of the roller press.
EP 1 261 431 B1 discloses an apparatus for grinding particulate material comprising a roller press or mill and an essentially vertically arranged shaft for feeding particulate material to the roller gap and having a downwardly increasing reduction in cross sectional circumference per height unit.
U.S. Pat. No. 6,517,016 B1 discloses a so-called belt roller mill comprising a plate conveyer belt guided continuously round a drive roller and a reversing roller and a grinding roller arranged vertically above the drive roller. A feeding device in the form of a feeding container feeds by means of the gravity particulate material to the upper run of the plate conveyer belt forming a layer i.e. a mat of material thereon. The belt transfers the material to a grinding gap between the upper grinding roller and the portion of the plate conveyer belt above the drive roller. It is to be assumed that the use of a plate conveyer entails many problems due to heavy load of the plate conveyer belt in the grinding zone where the planar plates cooperate with the cylindrical upper grinding roller and problems in guiding the planar plates over the lower drive roller.
U.S. Pat. No. 8,292,207 B2 discloses an apparatus for grinding of particulate material comprising a material feeding container delivering a layer i.e. mat of material essentially at the apex of the outer surface of a lower driven grinding roller. The lower grinding roller transfer the mat of material into a grinding gap formed between the lower roller and an upper grinding roller arranged in an offset manner above the lower grinding roller. The supply of the granular material to the outer surface of the lower roller and the delivery of the material to the grinding gap by means of the outer surface of lower roller is believed to create some problems and restrict the allowable peripheral velocity speed of the rollers and the throughput of the apparatus.